I have a Murena 2.2 at the moment that simply refuses to cool when it is idling, yet it is fine if you are driving it around and therefore the airflow through the radiator is fine, and the revs are generally 2,000 rpm or above. However, when it has to idle it, and engine temperature starts to rise, the fan switch doesn't cut in and it is because the coolant is not flowing to bring the heated coolant to the radiator! If you bring the revs up to say 1,500 rpm then the coolant starts to circulate and the switch will cut in, but you should not have to rev any of these engines to get sufficient circulation.

Now this car has a rebuilt engine, new radiator, new water pump, new 83 degree thermostat, and new radiator low rated fan switch (87/82 degree) and these all have been checked and work, so I pulled the water pump off as it was obviously not circulating the coolant at idle. In fact you could prove this lack of circulation by turning on the fan over-ride switch and the coolant and radiator would start to go cold yet the engine was still getting hotter!

When I got the pump off, it had an impeller I have not seen before and it is one of those alloy ones that I've heard about but never seen. It has seven curved vanes but they are not the right shape so they can't fit closely to the casing. The excess clearances between vanes and casing will result in a lack of pump efficiency. All my water pumps have always been the cast metal straight blade ones, and I've never had problems with those.

So has anyone else had experience of a Murena 2.2 fitted with the water pump that has the aluminium curved vane impeller, rather than the normal flat vane cast iron one? If you have, have you noticed a problem with cooling whilst idling for a long period such as in heavy traffic? Thanks.

I am about to swap it for a pump with the normal straight vane cast impeller and see if it cures the problem. I certainly hope so, as I have just about run out of ideas as to what is causing this. In thirty three years with 2.2 Murena I have never come across this before.

I sympathise with you Roy. I too have had all kinds of problems with cooling in my 2.2, ever since I got it. Mine overheated driving in a queue on the way home and blew out the rusted cooling pipes. For some reason the radiator fan switch did not cut in. I checked it when I changed to stainless pipes and it worked fine, so perhaps I too have had problems with the water pump.My pump was replaced half a year ago, because the bearing and seal wore out after sitting with no water, while I had the head rebuilt. This new pump has just failed with water running out around the seal and loosing all coolant when pressure rises. So today I am draining the water and getting ready for yet another pump. I have a new DOLZ pump from which we will use the shaft, bearing and seal. Jesper is helping me rebuild the pump and we will first check the one that just failed to see whet caused it to fail. It too was a rebuild using a DOLZ pump for parts. We will make sure it has the cast iron impeller with straight vanes.One option, that I know Anders Dinsen has (had) plans for, is an electric water pump, to be placed in the front compartment. I am also considering this as an option, in which case I would remove the impeller and, either remove the pulley and get a shorter fan-belt for just the alternator, or leave the pulley and just have no impeller.For now Jesper and I will find out why the pump failed so quickly and hopefully the replacement will last.Thank God I had not yet switched to Evans waterless coolant. That would have been expensive.

Just a few weeks ago I had something simulair on my 1.6.I know it's not a 2.2.I also swapped anything and if I keeped revs 1200 rpm no problem.I was suspecting waterpump to, and infact I had it ordered to place it before the meeting in Germanylast week.At some point I decided to change the cap on the expantion bottle as a last solution. ( don't ask me why, I was willing to try anything).Strange but true, it solved the problem.Drove 500 miles in the meeting with several traficjams without a problem.I don't know if it's the same with the 2,2 you are working on but why not try it.

Just a few weeks ago I had something simulair on my 1.6.I know it's not a 2.2.I also swapped anything and if I keeped revs 1200 rpm no problem.I was suspecting waterpump to, and infact I had it ordered to place it before the meeting in Germanylast week.At some point I decided to change the cap on the expantion bottle as a last solution. ( don't ask me why, I was willing to try anything).Strange but true, it solved the problem.Drove 500 miles in the meeting with several traficjams without a problem.I don't know if it's the same with the 2,2 you are working on but why not try it.

That's a good point Herman, and one I will certainly check out, thanks.

I've now built a new pump with one of the overhaul kits and modified the metal impeller (just needs 5mm removing from the boss) so that it can be fitted with the ceramic seal, so it should be a better pump than the original.

I sympathise with you Roy. I too have had all kinds of problems with cooling in my 2.2, ever since I got it. Mine overheated driving in a queue on the way home and blew out the rusted cooling pipes. For some reason the radiator fan switch did not cut in. I checked it when I changed to stainless pipes and it worked fine, so perhaps I too have had problems with the water pump.My pump was replaced half a year ago, because the bearing and seal wore out after sitting with no water, while I had the head rebuilt. This new pump has just failed with water running out around the seal and loosing all coolant when pressure rises. So today I am draining the water and getting ready for yet another pump. I have a new DOLZ pump from which we will use the shaft, bearing and seal. Jesper is helping me rebuild the pump and we will first check the one that just failed to see whet caused it to fail. It too was a rebuild using a DOLZ pump for parts. We will make sure it has the cast iron impeller with straight vanes.One option, that I know Anders Dinsen has (had) plans for, is an electric water pump, to be placed in the front compartment. I am also considering this as an option, in which case I would remove the impeller and, either remove the pulley and get a shorter fan-belt for just the alternator, or leave the pulley and just have no impeller.For now Jesper and I will find out why the pump failed so quickly and hopefully the replacement will last.Thank God I had not yet switched to Evans waterless coolant. That would have been expensive.

It will be interesting to hear if your water pump has the alloy impeller with the curved vanes, Jon.

Murena 2.2 should not have a cooling problem if they are all correct as the original design, and this is the first one I've had with a problem - and also the first I've seen with a pump with the alloy impeller. Seems too much of a coincidence to me.

It will be interesting to hear if your water pump has the alloy impeller with the curved vanes, Jon.

Murena 2.2 should not have a cooling problem if they are all correct as the original design, and this is the first one I've had with a problem - and also the first I've seen with a pump with the alloy impeller. Seems too much of a coincidence to me.

I hope you get yours sorted soon.

Roy

I checked with Jesper and we mounted the original straight vane impeller on the pump that is in the car. I have been checking closer regarding where the water is coming out and it appears that the axle seal is tight, but the hose on top of the pump is disintegrating and water is leaking out there. If true it will be a much easier job fixing the problem, as the pump won't have to come off. I have already managed to get the old hose off and it looks bad - swollen and spongy. Now to find a replacement. Simons want 26€ for one. It must be possible to find a universal hose with useable bends that will fit.

It will be interesting to hear if your water pump has the alloy impeller with the curved vanes, Jon.

Murena 2.2 should not have a cooling problem if they are all correct as the original design, and this is the first one I've had with a problem - and also the first I've seen with a pump with the alloy impeller. Seems too much of a coincidence to me.

I hope you get yours sorted soon.

Roy

I checked with Jesper and we mounted the original straight vane impeller on the pump that is in the car. I have been checking closer regarding where the water is coming out and it appears that the axle seal is tight, but the hose on top of the pump is disintegrating and water is leaking out there. If true it will be a much easier job fixing the problem, as the pump won't have to come off. I have already managed to get the old hose off and it looks bad - swollen and spongy. Now to find a replacement. Simons want 26€ for one. It must be possible to find a universal hose with useable bends that will fit.

Where did you find your "low rated" fan switch? The ones I can see at Simons, CarJoy, etc. do not mention the temperatures.

N.B. I sent an email reply to Jon earlier (as I could not log-in here for some reason) so he already knows the answer to this, but for others that read the forum I am adding it here anyway.

These switches are quite common and fitted to many older vehicles and there are also different switch settings for different applications. I do not use Simon or Carjoy for things like this, and one of the sources in the U.K. is Car Builder Solutions (see www.carbuildersolutions.com/uk/fan-switches ) for many common car items.

Looking at my pictures something catched my eye what may be of interest.The pulley's have different diameters.Tha alu impeller is the smallest.Maybe that's the cause.

Herman

Thanks Herman, you have provided the missing piece to this puzzle.

The pump fitted to the engine with the problem had the standard size pulley but had the alloy curved vane impeller. At engine idle the pump was not circulating the coolant so the engine would not cool, and the fan switch could not cut-in as the radiator was not getting the hot coolant. Now if it had had this smaller pulley, the pump would have been spinning faster, and that would have been enough to get the coolant circulating. We know this since, as I said in the original post, if we brought the engine revs up to 1,500 rpm it would start to circulate and the fan switch would finally cut-in.

So it appears that this pump with the different impeller should have had that smaller pulley. Since it did not and neither does a second one I have in my stock, dated exactly the same and presumably from the same batch, this means there are possibly more of these incorrectly made pumps around, which won't cool at idle. So please everyone beware, if you have a Murena 2.2 Dolz water pump (Part number T158) dated 12/96 and it has an alloy impeller with the No. 2B21302 cast into it, it needs a smaller pulley to drive it fast enough to cool the engine whilst standing idling.

The standard water pump pulley diameter is 120mm. I would say this smaller pulley needs to be about 90-100mm. Hopefully Herman will let us know the dimensions of that smaller pulley in the picture, when he has checked for us.

Thanks again Herman.

This smaller pulley also raises another point. With the smaller pulley, I think the vee-belt will need to be shorter too.